Data protection officials are bewildered by the German federal prosecutor's decision not to start a criminal investigation into the alleged mass surveillance of German citizens by the U.S. National Security Agency (NSA).

The German federal prosecutor did not find enough evidence to warrant a criminal investigation, German media reported Wednesday, citing sources within the federal prosecutor's office.

There will be no investigation into the alleged mass surveillance of German citizens, nor will there be an investigation into the NSA's alleged spying on German Chancellor Angela Merkel's phone, the reports said. Documents to terminate the preliminary investigations, which were in the works for months, are ready but not yet signed, according to the reports.

The federal prosecutor has not yet made a final decision but will make one soon, a spokesman for his office said Wednesday, adding that there are still some loose ends to tie up. However, he did not deny that the investigations would be terminated.

It was impossible for the federal prosecutor to gather evidence about the German activities of the NSA and its British counterpart GCHQ because of a lack of witnesses and documents, according to the SA1/4ddeutsche Zeitung. Requests filed with U.S. authorities probably went unanswered and attempts to get information from the German government and intelligence services were denied. The authorities invariably told the investigators that they only had information based on media reports, the newspaper said.

Der Spiegel, which revealed the spying on Merkel's phone, refused to provide the prosecution with documents from former NSA contractor Edward Snowden citing source protection, according to the newspaper. The prosecution's efforts to retrieve documents from Snowden's archive or get a written opinion from him were also in vain, it added.

The reports on the termination of the investigations were received "with bewilderment" at the Office of the Data Protection Commissioner (ULD) for the German state of Schleswig-Holstein.

Given that there are currently three books available from German journalists who have access to Snowden's documents, and an ongoing stream of news reports on the global disregard for data protection it is "completely incomprehensible" why the prosecution apparently did not even try to question known suspects, said ULD's data protection commissioner Thilo Weichert .

The work of data protection authorities "will be reduced to absurdity" if they are expected to function when the top German investigatory authority stops a preliminary investigation while the privacy of millions of German citizens is obviously violated, Weichert said.

"The fact that these investigations are technically extremely complex and new legal territory should not be an obstacle but an incentive to enforce the law," he said, adding that public statements from NSA and GCHQ alone should be enough to warrant an investigation.

If the attorney general indeed refuses to open an investigation this borders on a refusal to work, said Digitalcourage's Rena Tangens in an email, calling the situation "grotesque." Privacy and human rights group Digitalcourage filed a criminal complaint against the German federal government for its alleged involvement in illegal and prohibited covert intelligence activities.

Loek is Amsterdam Correspondent and covers online privacy, intellectual property, open-source and online payment issues for the IDG News Service. Follow him on Twitter at @loekessers or email tips and comments to loek_essers@idg.com